Longitudinal Bedside Assessments of Brain Networks in Disorders of Consciousness: Case Reports From the Field

Abstract

Clinicians are regularly faced with the difficult challenge of diagnosing consciousness after severe brain injury. As such, as many as 40% of minimally conscious patients who demonstrate fluctuations in arousal and awareness are known to be misdiagnosed as unresponsive/vegetative based on clinical consensus. Further, a significant minority of patients show evidence of hidden awareness not evident in their behavior. Despite this, clinical assessments of behavior are commonly used as bedside indicators of consciousness. Recent advances in functional high-density electroencephalography (hdEEG) have indicated that specific patterns of resting brain connectivity measured at the bedside are strongly correlated with the re-emergence of consciousness after brain injury. We report case studies of four patients with traumatic brain injury who underwent regular assessments of hdEEG connectivity and Coma Recovery Scale-Revised (CRS-R) at the bedside, as part of an ongoing longitudinal study. The first, a patient in an unresponsive wakefulness state (UWS), progressed to a minimally-conscious state several years after injury. HdEEG measures of alpha network centrality in this patient tracked this behavioral improvement. The second patient, contrasted with patient 1, presented with a persistent UWS diagnosis that paralleled with stability on the same alpha network centrality measure. Patient 3, diagnosed as minimally conscious minus (MCS–), demonstrated a significant late increase in behavioral awareness to minimally conscious plus (MCS+). This patient's hdEEG connectivity across the previous 18 months showed a trajectory consistent with this increase alongside a decrease in delta power. Patient 4 contrasted with patient 3, with a persistent MCS- diagnosis that was similarly tracked by consistently high delta power over time. Across these contrasting cases, hdEEG connectivity captures both stability and recovery of behavioral trajectories both within and between patients. Our preliminary findings highlight the feasibility of bedside hdEEG assessments in the rehabilitation context and suggest that they can complement clinical evaluation with portable, accurate and timely generation of brain-based patient profiles. Further, such hdEEG assessments could be used to estimate the potential utility of complementary neuroimaging assessments, and to evaluate the efficacy of interventions.

Resting-State Electroencephalography for Prognosis in Disorders of Consciousness Following Traumatic Brain Injury

“…One study reported no associations between spectral measures and outcome within days of initial TBI (18). In addition, one study reported positive associations between alpha and beta measures and first-year recovery from UWS (28), and two reported associations between either gamma [negative association; (29)] or alpha and delta measures [positive and negative associations respectively; (30)] with recovery from UWS or MCS, in patients tested months or years after TBI.…”

“…Third, the existing literature has not systematically tested the prognostic value of different EEG measures; many studies have selected only one or two EEG metrics [e.g., (20,21,30)]. Some have used more complex metrics, drawn from network approaches, which do not have an intuitive correspondence to the more commonly reported spectral measures (30). Given the more complex analyses required for these approaches, it will be important to assess their advantages over simpler measures.…”

Competitive Frontoparietal Interactions Mediate Implicit Inferences

“…Consistencies of the difference of time-frequency phase values between two channels in the alpha band across trials were computed [intersite phase clustering (ISPC); Siegel et al, 2012;Cohen, 2014]. We chose P4 as our "seed" electrode based on previous studies demonstrating the involvement of right parietal cortex in attention and alpha oscillations (Bareham et al, 2018). We used the same preprocessing steps as described above for the time-frequency analyses and a baseline period of Ϫ300 to 0 ms before cue onset for both cue types.…”

Deciding Under Uncertainty: The Case of Refractory Intracranial Hypertension

“…Natural history of recovery from brain injury can be significantly longer than what is usually recorded and reported. Contemporary series with extended follow-ups provide encouraging data in terms of recovery potential beyond the first year from injury, and show that GOSE categories as reported from trials are not necessarily static end-states (30,31). In terms of DC, surrogates should be also informed about the need of additional future surgery such as cranioplasty, which carries both promise in terms of neurologic function improvement, and concern due to its own moribidity and complications (32).…”